JP6828437B2 - Adhesive film and adhesive film roll - Google Patents

Description

The present invention relates to an adhesive film which is excellent in surface smoothness and excellent in slipperiness, handleability and winding property, and can be suitably used as a surface protective film.

Adhesive films that have adhesiveness to the surface of the adherend and can be peeled off without contaminating the adherend after use are used as packaging films, surface protection films, and process films, and are used in various machines. It is widely used as a protective film for processing, storage, transportation, shipping, etc. by being attached to the surface of products, display panel members, synthetic resin panels, and protected objects such as substrates and parts of electrical equipment. It is used.

As such an adhesive film, for example, Patent Documents 1 and 2 describe a film in which an adhesive is applied to the surface of a polyethylene terephthalate film or the like. As in Patent Documents 1 and 2, an adhesive layer is coated offline on a smooth film and dried, and since the adhesive film has low slipperiness and is difficult to wind up, a separator such as a release film is used. It is common to wind it up as paper. However, the use of interleaving paper not only increases the cost, but also requires a rewinding facility for the interleaving paper when the adhesive film is unwound and used, so that the productivity cannot be said to be sufficient.

Japanese Unexamined Patent Publication No. 2007-131661 International Publication No. 2012/128010

An object of the present invention is to solve the above-mentioned problems. That is, it is an object of the present invention to provide an adhesive film having excellent surface smoothness and excellent slipperiness, handleability and winding property.

In order to solve the above-mentioned problems and achieve the object, the adhesive film of the present invention is an adhesive film in which an adhesive layer is provided on one side of a base film containing polypropylene as a main component, and the back surface of the base film ( The ten-point average roughness SRz of the surface on which the adhesive layer is not provided) is 3,000 nm or less, and the thickness d of the adhesive layer d is 3,000 nm or less.

Since the adhesive film of the present invention is excellent in surface smoothness, slipperiness, handleability, and winding property, it can be suitably used as a surface protective film.

The adhesive film of the present invention is an adhesive film in which an adhesive layer is provided on one side of the base film, and the ten-point average roughness SRz of the back surface (the surface without the adhesive layer) of the base film is 3,000 nm or less. Is. It is more preferably 2,500 nm or less, further preferably 2,000 nm or less, and most preferably 1,500 nm or less. If the ten-point average roughness SRz on the back surface of the base film exceeds 3,000 nm, the surface shape of the adhesive film may be transferred to the surface of the adherend when the film is bonded to the adherend as a protective film and wound up. is there. Further, when the adherend is made of a soft material or when defect detection is performed while the adherend is attached to the adherend, further surface smoothness may be required, and SRz is more preferably 1,000 nm. Below, it is more preferably 500 nm or less, and most preferably 300 nm or less. From the viewpoint of transfer of the surface shape of the adhesive film, it is preferable that the SRz is small, but if the ten-point average roughness SRz on the back surface of the base film is too small, the slipperiness with the surface of the adhesive layer deteriorates and winding is difficult. Therefore, the lower limit of SRz is about 30 nm. As a method in which SRz is within the above range, a known technique can be used, a method of blending two or more kinds of raw materials to form surface irregularities, a method of adding slippery particles to the surface layer, or an unstretched film. A method of forming two or more different crystal morphologies and forming irregularities at the time of stretching can be used. Further, in order to use a polypropylene film as the base film and to set SRz in the above range, the raw material composition of the film and the laminated composition of the film should be set in the range described later, and the cast (melt-extruded resin) at the time of film formation should be set. It is preferable that the conditions (sheeting step) and the longitudinal stretching conditions are within the range described later, and the β crystals of the cast sheet are reduced.

In the pressure-sensitive adhesive film of the present invention, the thickness d of the pressure-sensitive adhesive layer is 3,000 nm or less. It is more preferably 1,200 nm or less, further preferably 800 nm or less, still more preferably 600 nm or less, and most preferably 400 nm or less. If the thickness d of the adhesive layer exceeds 3,000 nm, the surface of the adhesive layer becomes smooth, the slipperiness between the back surface of the base film and the surface of the adhesive layer deteriorates, and winding may become difficult. In addition, the adhesive layer may be lined off. “Bleed” means that after applying a solution of an adhesive layer on one side of a base film, it is dried and cured in a drying furnace, and the adhesive film of the present invention is wound into a roll without passing through a release film. This refers to a phenomenon in which a part of the adhesive layer is transferred to the back surface of the base film when the adhesive film is unwound during use. If the thickness d of the adhesive layer exceeds 3,000 nm, the adhesive layer may not be sufficiently dried in the drying oven, and lining may occur. A known technique can be used as a method for setting the thickness of the adhesive layer within the above range, and it can be controlled by adjusting the solid content concentration of the solution of the adhesive layer and the coating thickness in various coating methods. If the thickness of the adhesive layer is too thin, stable coating may be difficult, or the adhesive strength may be too low to adhere to the adherend. Therefore, the lower limit is about 100 nm.

The pressure-sensitive adhesive film of the present invention preferably has a center average surface roughness SRa of the back surface of the base film of 100 nm or less. It is more preferably 40 nm or less, further preferably 30 nm or less, and most preferably 25 nm or less. If the center average surface roughness SRa on the back surface of the base film exceeds 100 nm, the surface shape of the adhesive film may be transferred to the surface of the adherend when the film is bonded to the adherend as a protective film and wound up. From the viewpoint of transfer of the surface shape of the adhesive film, the smaller the SRa, the more preferable, but the lower limit of the SRa is practically about 1 nm. As a method of setting SRa in the above range, a known technique can be used, a method of blending two or more kinds of raw materials to form surface irregularities, a method of adding slippery particles to the surface layer, or an unstretched film. A method of forming two or more different crystal morphologies and forming irregularities at the time of stretching can be used. Further, in order to use a polypropylene film as the base film and set SRa in the above range, the raw material composition of the film and the laminated structure of the film are set in the range described later, and the casting condition and the longitudinal stretching condition are set in the range described later. , It is preferable to reduce the β crystals of the cast sheet.

In the pressure-sensitive adhesive film of the present invention, the ratio of the ten-point average roughness SRz on the back surface of the base film to the thickness d of the pressure-sensitive adhesive layer, and the value of SRz / d are preferably 0.1 to 3.5. It is more preferably 0.3 to 3.5, still more preferably 0.5 to 3.0. If the value of SRz / d is less than 0.1, the slipperiness between the back surface of the base film and the surface of the adhesive layer may deteriorate and winding may become difficult. When the SRz / d value exceeds 3.5, the SRz value becomes large, and the surface shape of the adhesive film may be transferred to the surface of the adherend when the film is bonded to the adherend as a protective film and wound up. is there.

By setting the surface roughness of the base film and the thickness of the adhesive layer within the above-mentioned ranges, the adhesive film of the present invention has high surface smoothness, yet has a certain adhesive strength, and is slippery. It is possible to obtain an adhesive film that is excellent in handleability and winding property and does not cause lining. In the conventional adhesive film, since the adhesive layer is thick, the slipperiness between the back surface of the base film and the surface of the adhesive layer is poor, and it is difficult to wind up with good quality without a release film. Further, in the conventional adhesive film, a solution of the adhesive layer is applied on the base film, dried in a drying furnace to the extent that the adhesive layer does not adhere to the transport roll, and wound into a roll together with the release film. A general method was to accelerate the curing of the adhesive layer by aging after removal. However, in this method, if the film is wound without a release film, the adhesion between the back surface of the base film and the adhesive layer becomes high at the time of curing, which may cause lining.

In the present invention, by making the thickness of the adhesive layer sufficiently thinner than the conventional one, it is possible to achieve both adhesiveness and slipperiness even when a smooth base film is used, and further, the adhesive layer is cured in a drying furnace. It has become possible to sufficiently advance the process, and it has become possible to provide an adhesive film that is unlikely to be lined off even if it is wound up without using a release film.

The pressure-sensitive adhesive film of the present invention preferably has a haze of 10% or less. It is more preferably 5% or less, further preferably 2% or less, and most preferably 1% or less. If the haze exceeds 10%, the surface roughness of the film surface is large, and the surface shape may be transferred to the adherend. The lower the haze is, the more preferable it is from the viewpoint of transparency, but practically, the lower limit is about 0.05%. In order to set the haze within the above range, the raw material composition of the film and the laminated composition of the film are set to the ranges described later to prevent deterioration of transparency due to particles and the like, and the casting conditions and the longitudinal stretching conditions at the time of film formation are described later. It is preferable to keep the range within the range of the cast sheet to reduce β crystals.

Adhesive film of the present invention is preferably the longitudinal direction of the Young's modulus E _MD is not less than 1 GPa. When the longitudinal direction of the Young's modulus E _MD of less than 1 GPa, torn stretches the film with a release tension upon the release from the adherend used as a surface protective film, there is a case where peeling trace remains on the adherend. In addition, the film may be stretched due to the transport tension at the time of bonding. The E _MD is more preferably 1.2 GPa or more, still more preferably 1.4 GPa or more. The stronger the E _MD, the more preferable, but practically, the upper limit is about 10 GPa. In order to set the value of _{EMD in} the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described later, and the film is biaxially stretched at a high magnification to obtain a base film. Is preferable.

Adhesive film of the present invention is preferably a Young's modulus E _TD in the transverse direction is not less than 1 GPa. When E _TD is less than 1 GPa, or become a film easily wrinkles on during transport, wound into a roll is pasted to a film as an adherend, such as wrinkles on the roll by the dimensional change of the film upon storage It may occur. E _TD is more preferably 1.5GPa or more, more preferably 2.0GPa or more, and most preferably at least 2.5 GPa. E _TD is preferably as strong, in effect an upper limit of about 10 GPa. In order to set the value of _{ETD in} the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described later, and the film is biaxially stretched at a high magnification to obtain a base film. Is preferable.

In the present application, the direction parallel to the film forming direction is referred to as the film forming direction, the longitudinal direction, or the MD direction, and the direction orthogonal to the film forming direction in the film surface is referred to as the width direction or the TD direction.

The pressure-sensitive adhesive film of the present invention preferably has a heat shrinkage rate of 1.0% or less after heat treatment at 110 ° C. in the width direction. More preferably, it is 0.8% or less, further preferably 0.5% or less, and most preferably 0.3% or less. If the heat shrinkage rate in the width direction exceeds 1.0%, the film will be deformed and peeled off or wrinkled, for example, when it is bonded to another material and then passed through a drying process in which heat is applied. In some cases. Further, when the film is attached to the adherend and wound into a roll and stored, if the environmental temperature rises, the roll may be wrinkled due to a change in the size of the film. The lower limit of the heat shrinkage rate is not particularly limited, but the film may expand, and the lower limit is substantially −2.0%. In order to set the heat shrinkage rate in the above range, the raw material composition of the film should be in the range described later, the film forming conditions should be in the range described later, and the heat fixing and relaxation conditions after biaxial stretching should be in the range described later. Is effective. Here, the heat shrinkage rate is defined by cutting out five samples having a width of 10 mm and a length of 200 mm (measurement direction) in the width direction of the film, marking them as marked lines at positions 25 mm from both ends, and using a universal projector. The distance between the marked lines is measured to set the test length (l ₀ ), then the test piece is sandwiched between papers, placed in an oven kept at 110 ° C with no load, heated for 60 minutes, taken out, and cooled at room temperature. After that, the dimension (l ₁ ) was measured with a universal projector and calculated by the following formula, and the average value of 5 pieces was taken as the heat shrinkage rate.

Heat shrinkage = {(l _{0 −} l ₁ ) / l ₀ } × 100 (%)
The pressure-sensitive adhesive film of the present invention preferably has a peeling force at 180 ° C. of 1 N / 25 mm or less after being attached to a glass plate. The peeling force is more preferably 0.5 N / 25 mm or less, further preferably 0.2 N / 25 mm or less, and most preferably 0.05 N / 25 mm or less. If the peeling force exceeds 1 N / 25 mm, the slipperiness between the back surface of the base film and the surface of the adhesive layer deteriorates, which may make winding difficult or line-off may occur. In order to set the peeling force in the above range, the composition and thickness of the adhesive layer are set in the range described later, and the raw material composition and film forming conditions of the film are set in the range described later, and the surface roughness of the base film is controlled. Is effective. If the peeling force is less than 0.01 N / 25 mm, the adhesive film may peel off during transportation after bonding with the adherend, so the lower limit is about 0.01 N / 25 mm.

The thickness of the pressure-sensitive adhesive film of the present invention is appropriately adjusted depending on the intended use and is not particularly limited, but is preferably 5 μm or more and 100 μm or less. If the thickness is less than 5 μm, handling may be difficult, and if it exceeds 100 μm, the amount of resin may increase and productivity may decrease. Even if the thickness of the adhesive film of the present invention is reduced, the adhesive film has excellent strength (Young's modulus) and can maintain handleability. In order to take advantage of such characteristics, the thickness is more preferably 5 μm or more and 40 μm or less, further preferably 5 μm or more and 30 μm or less, and most preferably 5 μm or more and 25 μm or less. The thickness can be adjusted by adjusting the screw rotation speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretching ratio, and the like within a range that does not deteriorate other physical properties.

As the base film used for the adhesive film of the present invention , known materials such as polyamide, aramid, polyimide, polyamideimide, cellulose, polypropylene, polyethylene, polymethylpentene, nylon, and polyethylene terephthalate are used alone or in combination of two or more. However, it is a base film because it has excellent surface smoothness, a high-quality film with few fish eyes and foreign substances can be obtained, and handling properties such as film strength and stiffness can be improved. There is preferably made as a main component polypropylene emissions. Here, in the present application, the "main component" means that the ratio of the specific component to all the components is 50% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more. Most preferably, it is 99% by mass or more . By using polypropylene as the main component of the base film, the excellent mold releasability of polypropylene is utilized to improve the slipperiness between the back surface of the base material layer and the surface of the adhesive layer, and the adhesive has excellent handleability and winding property. You can get the film.

Next, the base film used for the pressure-sensitive adhesive film of the present invention will be described by taking the case where a polypropylene film is used as the base film as an example.

The polypropylene raw material of the polypropylene film used for the pressure-sensitive adhesive film of the present invention is not particularly limited as long as the above-mentioned physical properties are satisfied, but it is preferable to use crystalline polypropylene (hereinafter, polypropylene raw material A) from the viewpoint of strength and heat resistance.

The polypropylene raw material A is preferably polypropylene having a cold xylene-soluble portion (hereinafter, CXS) of 4% by mass or less and a mesopentad fraction of 0.90 or more. If these conditions are not satisfied, the film forming stability may be inferior, the strength of the film may be lowered, and the dimensional stability and heat resistance may be significantly lowered.

Here, the cold xylene-soluble portion (CXS) refers to a polypropylene component dissolved in xylene when the sample is completely dissolved in xylene and then precipitated at room temperature, and has low stereoregularity. It is considered that it corresponds to a component that is difficult to crystallize because of its low molecular weight. If a large amount of such a component is contained in the resin, the thermal dimensional stability of the film may be inferior. Therefore, the CXS is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. The lower the CXS, the more preferable, but the lower limit is about 0.1% by mass. In order to obtain polypropylene having such CXS, a method of increasing the catalytic activity when obtaining the resin, a method of washing the obtained resin with a solvent or the propylene monomer itself, a method of using metallocene PP, or the like can be used.

From the same viewpoint, the mesopentad fraction of the polypropylene raw material A is preferably 0.90 or more, and more preferably 0.94 or more. The mesopentad fraction is an index showing the stereoregularity of the polypropylene crystal phase measured by nuclear magnetic resonance spectroscopy (NMR method), and the higher the value, the higher the crystallinity, the higher the melting point, and the higher the temperature. This is preferable because it increases dimensional stability. In addition, the releasability of the film surface is increased, and the adhesive layer is less likely to be lined out, which is preferable. The upper limit of the mesopentad fraction is not specified. In order to obtain a resin having such high stereoregularity, a method of washing the resin powder obtained with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or a co-catalyst, a method of appropriately selecting a composition, and the like are used. It is preferably adopted.

Further, as the polypropylene raw material A, the melt flow rate (MFR) is more preferably 1 to 10 g / 10 minutes (230 ° C., 21.18 N load), and particularly preferably 2 to 5 g / 10 minutes (230 ° C., 21.18 N). The one in the range of (load) is preferable from the viewpoint of film forming property and film strength. In order to set the melt flow rate (MFR) to the above value, a method of controlling the average molecular weight or the molecular weight distribution is adopted.

The polypropylene raw material A is mainly composed of a homopolymer of propylene, but may contain a copolymerization component due to other unsaturated hydrocarbons as long as the object of the present invention is not impaired, and propylene is not alone. The coalescence may be blended. Examples of the monomer components constituting such copolymerization components and blends include ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene. 1,1-Hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2- Norbornene and the like can be mentioned. From the viewpoint of dielectric breakdown resistance and dimensional stability, the copolymerization amount or blend amount is preferably less than 1 mol% in terms of copolymerization amount and less than 10% by mass in terms of blend amount.

Further, the biaxially oriented polypropylene film used for the pressure-sensitive adhesive film of the present invention may contain branched-chain polypropylene H from the viewpoint of improving strength and dimensional stability in addition to the above-mentioned polypropylene raw material A. The branched-chain polypropylene H referred to here is polypropylene having 5 or less internal tri-substituted olefins per 10,000 carbon atoms. The presence of this internal trisubstituted olefin can be confirmed by the proton ratio of the ¹ H-NMR spectrum. When it is contained, it is preferably 0.05 to 10% by mass, more preferably 0.5 to 8% by mass, and further preferably 1 to 5% by mass. By containing the branched chain polypropylene H, the size of spherulite formed in the cooling (casting) step of the melt-extruded resin sheet can be controlled to be small, and a polypropylene film having excellent transparency, strength and surface smoothness can be obtained. it can.

As the branched chain polypropylene H, the melt flow rate (MFR) is preferably in the range of 1 to 20 g / 10 minutes, and more preferably in the range of 1 to 10 g / 10 minutes from the viewpoint of film forming property. preferable. Further, the melt tension is preferably in the range of 1 to 30 cN, and more preferably in the range of 2 to 20 cN.

The polypropylene film used for the pressure-sensitive adhesive film of the present invention preferably has an ethylene component content of 10% by mass or less in the polymer constituting the film. It is more preferably 5% by mass or less, still more preferably 3% by mass or less. The higher the content of the ethylene component, the lower the crystallinity and the easier it is to improve the transparency. However, if the content of the ethylene component exceeds 10% by mass, the strength is lowered or the heat resistance is lowered to heat. The shrinkage rate may worsen. In addition, the releasability of the film surface may decrease, and the adhesive layer may be easily lined off.

From the viewpoint of transparency, heat resistance, and strength, the polypropylene film used for the pressure-sensitive adhesive film of the present invention preferably contains 95% by mass or more of the polypropylene polymer contained in the polymer constituting the film. It is more preferably 96% by mass or more, further preferably 97% by mass or more, and most preferably 98% by mass or more.

The polypropylene raw material used for the pressure-sensitive adhesive film of the present invention includes various additives such as a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, and an antiblocking agent, as long as the object of the present invention is not impaired. It can also contain a filler, a viscosity modifier, an anticoloring agent and the like.

Among these, the selection of the type and amount of the antioxidant is important from the viewpoint of bleeding out of the antioxidant. That is, the antioxidant is a phenolic agent having steric hindrance, and at least one of them is preferably a high molecular weight type having a molecular weight of 500 or more. Specific examples thereof include various examples. For example, 1,3,5-trimethyl-2,4,6-with 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4). Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (eg, BASF's Irganox® 1330: molecular weight 775.2) or tetrakis [methylene-3 (3,5-di-t-) Butyl-4-hydroxyphenyl) propionate] methane (for example, Irganox (registered trademark) 1010 manufactured by BASF Corporation: molecular weight 1177.7) or the like is preferably used in combination. The total content of these antioxidants is preferably in the range of 0.03 to 1.0% by mass with respect to the total amount of the polypropylene raw material. If the amount of the antioxidant is too small, the polymer may deteriorate in the extrusion process, the film may be colored, or the long-term heat resistance may be poor. If too much antioxidant is used, bleeding out of these antioxidants may reduce transparency. A more preferable content is 0.05 to 0.9% by mass, and particularly preferably 0.1 to 0.8% by mass.

A crystal nucleating agent can be added to the polypropylene raw material used for the pressure-sensitive adhesive film of the present invention within a range not contrary to the object of the present invention. As described above, the branched chain polypropylene (H) already has an α-crystal or β-crystal crystal nucleating agent effect by itself, but another type of α-crystal nucleating agent (dibenzylidene sorbitols, sodium benzoate, etc.) ), Β-crystal nucleating agent (amide compound such as potassium 1,2-hydroxystearate, magnesium benzoate, N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide, quinacridone compound, etc.) and the like. .. However, since excessive addition of the above-mentioned other type of nucleating agent may cause a decrease in stretchability and a decrease in transparency and strength due to void formation, etc., the addition amount is usually 0.5% by mass or less, preferably 0.1. It is preferably mass% or less, more preferably 0.05 mass% or less.

The polypropylene film used for the pressure-sensitive adhesive film of the present invention can be obtained by, for example, biaxially stretching using the above-mentioned raw materials. The biaxial stretching method can be obtained by any of the simultaneous biaxial stretching method for inflation, the simultaneous biaxial stretching method for stenters, and the sequential biaxial stretching method for stenters. Among them, film forming stability, thickness uniformity, and film It is preferable to adopt the stenter sequential biaxial stretching method in terms of controlling high rigidity and dimensional stability.

The polypropylene film used for the adhesive film of the present invention may have slipperiness improved by using slippery particles or the like on the surface layer. In such a case, the film is composed of at least two layers of the surface layer (I) and the base layer (II), and the surface layer (I) contains particles, and the average particle diameter thereof is 0.7 μm or less. preferable. If the average particle size exceeds 0.7 μm, the surface roughness may increase and the surface smoothness may decrease. In addition, when voids are likely to be generated at the particle interface during stretching, the transparency is lowered, or the particles added to the surface layer (I) fall off during film formation, the surface roughness is increased, and the haze is increased. There is. The average particle size is more preferably 0.5 μm or less, and further preferably 0.2 μm or less. From the viewpoint of surface smoothness, it is preferable that the average particle size is small, but if it is less than 0.05 μm, the slipperiness may be deteriorated or the particles may be aggregated into coarse particles and the transparency may be lowered. Further, from the viewpoint of improving handleability, two or more kinds of particles having different average particle diameters may be used in combination as a raw material. For the average particle size, the film was dissolved in hot xylene at 135 ° C., the insoluble matter was photographed with a scanning electron microscope (3,000 times), and the particle size (major axis diameter) was measured for 50 observed particles. It is the average value at the time of measurement. The particles used for the surface layer (I) are not particularly limited as long as they do not impair the effects of the present invention, and the inorganic particles include silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, and zeolite particles. As the organic particles, acrylic resin particles, styrene resin particles, polyester resin particles, polyurethane resin particles, polycarbonate resin particles, polyamide resin particles, silicone resin particles, fluorine resin particles, or the above resin Examples thereof include copolymer resin particles of two or more kinds of monomers used for the synthesis of. However, since polypropylene resin has a low surface energy, when particles are added and stretched, the particle interface is peeled off during stretching to generate voids, which may increase haze and reduce transparency. From the viewpoint of improving transparency, the surface of the particles is preferably hydrophobic, and it is preferable to use the above-mentioned inorganic particles or organic particles having a silane coupling treatment on the surface, particularly silicone particles or silica particles having a silane coupling treatment. Is preferable.

Further, from the viewpoint of preventing the above-mentioned particles from falling off, it is preferable that the particle size distribution of the particles used is as narrow as possible. From this point of view, it is preferable to use silica particles produced by the sol-gel method as the silica particles, and it is preferable to use silicone particles, acrylic resin particles, or styrene resin particles produced by the polymerization method as the organic particles.

The polypropylene film used for the pressure-sensitive adhesive film of the present invention preferably has a particle content of the surface layer (I) of 0.01 to 1.0% by mass. If the content is less than 0.01% by mass, the effect of reducing the friction coefficient may not be obtained. If the content exceeds 1.0% by mass, the haze may increase and the transparency may decrease. The content is more preferably 0.05 to 0.7% by mass, further preferably 0.05 to 0.65% by mass, and most preferably 0.1 to 0.6% by mass.

Next, a method for producing a polypropylene film used for the pressure-sensitive adhesive film of the present invention will be described, but the present invention is not necessarily limited thereto.

First, 98 parts by mass of polypropylene raw material A and 2 parts by mass of silica particles are put into a twin-screw extruder to prepare a 2% by mass master raw material of silica particles. 25 parts by mass of the master raw material and 75 parts by mass of the polypropylene raw material A are dry-blended and supplied to the single-screw extruder for the A layer (surface layer (I)), and the polypropylene raw material A is single-screw for the B layer (base layer (II))). It is supplied to an extruder and melt-extruded at 200 to 260 ° C. Then, after removing foreign substances and modified polymers with a filter installed in the middle of the polymer tube, the laminated thickness ratio becomes 1/22/1 with a multi-manifold type A layer / B layer / A layer composite T die. As described above, the mixture is discharged onto a casting drum to obtain a laminated unstretched sheet having a layer structure of A layer / B layer / A layer. At this time, the surface temperature of the casting drum is preferably 10 to 40 ° C. from the viewpoint of transparency. Further, a two-layer laminated structure of A layer / B layer may be used.

As the adhesion method to the casting drum, any of the electrostatic application method, the adhesion method using the surface tension of water, the air knife method, the press roll method, the underwater casting method, etc. may be used, but the flatness is high. The air knife method, which is good and can control the surface roughness, is preferable. The air temperature of the air knife is 0 to 50 ° C., preferably 0 to 30 ° C., and the blowing air speed is preferably 130 to 150 m / s. Further, it is preferable to appropriately adjust the position of the air knife so that air flows to the downstream side of the film formation so as not to cause vibration of the film.

Further, by forcibly cooling the non-casting drum surface of the film after being brought into close contact with the casting drum, β crystal formation on the non-casting drum surface can be suppressed, and the smoothness and transparency of the film are improved. be able to. The non-casting drum surface may be cooled by any of air cooling by air, press roll method, underwater casting method, etc., but the equipment is simple, the surface roughness can be easily controlled, and the smoothness is high. Air cooling with good air is preferred.

The obtained unstretched sheet is introduced into the longitudinal stretching step. In the longitudinal stretching step, first, the unstretched sheet is brought into contact with a plurality of metal rolls kept at 120 ° C. or higher and lower than 150 ° C., preheated, heated to the stretching temperature, stretched 3 to 8 times in the longitudinal direction, and then to room temperature. Cooling. When the stretching temperature is 150 ° C. or higher, the orientation of the film becomes weak and the strength may decrease. If the draw ratio is less than 3 times, the orientation of the film becomes weak and the strength may decrease.

Next, the longitudinally uniaxially stretched film is guided to a tenter, the edge of the film is gripped with a clip, and the film is laterally stretched 7 to 13 times in the width direction at a temperature of 140 to 165 ° C. If the stretching temperature is low, the film may break or the transparency may decrease, and if the stretching temperature is too high, the orientation of the film may be weak and the strength may decrease. Further, if the magnification is high, the film may break, and if the magnification is low, the orientation of the film may be weak and the strength may decrease.

In the subsequent heat treatment and relaxation treatment steps, while tensioning the width direction with a clip and giving relaxation at a relaxation rate of 2 to 20% in the width direction, heat fixing is performed at a temperature of 100 ° C. or higher and lower than 160 ° C., and the width direction is fixed with a clip. Is guided to the outside of the tenter through a cooling step at 80 to 100 ° C. while being tensely gripped, the clip at the end of the film is released, the film edge is slit in the winder step, and the film product roll is wound.

Next, the adhesive layer used for the adhesive film of the present invention will be described.

The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film of the present invention is not particularly limited, and rubber-based, vinyl polymerization-based, condensation polymerization-based, thermosetting resin-based, silicone-based, and the like can be used.

Among these, examples of the rubber-based pressure-sensitive adhesive include a butadiene-styrene copolymer system, a butadiene-acrylonitrile copolymer system, and an isobutylene-isoprene copolymer system. Examples of the vinyl polymerization type pressure-sensitive adhesive include an acrylic type, a styrene type, a vinyl acetate-ethylene copolymer system, and a vinyl chloride-vinyl acetate copolymer system. Further, as the condensation polymerization type pressure-sensitive adhesive, a polyester type can be mentioned. Further, examples of the thermosetting resin-based adhesive include an epoxy resin-based adhesive and a urethane resin-based adhesive.

Among these, an acrylic pressure-sensitive adhesive is preferably used in consideration of excellent transparency, weather resistance, heat resistance, moisture heat resistance, substrate adhesion, and the like. Specific examples of such an acrylic pressure-sensitive adhesive include SK Dyne (registered trademark) 1310, 1435, SK Dyne 1811L, SK Dyne 1888, SK Dyne 2094, SK Dyne 2096, SK Dyne 2137, and SK Dyne 3096 manufactured by Soken Kagaku Co., Ltd. , SK Dyne 1852 and the like are preferred examples.

Further, it is preferable to use a curing agent together with the acrylic pressure-sensitive adhesive. Specific examples of the curing agent include toluene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, and diphenylmethane-4 in the case of isocyanate. -4'-diisocyanate, diphenylmethane-2-4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4-4'-diisocyanate, dishikiurohexylmethane-2-4'-diisocyanate , Lysine isocyanate and the like. The mixing ratio of the curing agent is 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive. If it is less than 0.1 part by mass, the pressure-sensitive adhesive layer is not sufficiently cured in the drying furnace, and lining may occur. If it exceeds 10 parts by mass, the excess curing agent may be transferred to the substrate or gasified at a high temperature to cause contamination.

Further, depending on the material of the adherend (glass or functional film), the acrylic pressure-sensitive adhesive may be appropriately added with an antioxidant, an ultraviolet absorber, a silane coupling agent, a metal deactivator, or the like. ..

Next, a method for producing an adhesive layer of the adhesive film of the present invention will be described, but the present invention is not necessarily limited to this.

First, a coating agent for the adhesive layer is prepared. The coating agent can be used by dissolving the above-mentioned additives such as a pressure-sensitive adhesive and a curing agent in a solvent. The solvent can be appropriately adjusted depending on the drying temperature of the coater, the viscosity of the coating material, and the like. Specific examples thereof include methanol, ethanol, isopropyl alcohol, n-butanol, tert-butanol, ethylene glycol monomethyl ether, and 1 -At least one solvent selected from methoxy-2-propanol, propylene glycol monomethyl ether, cyclohexanone, toluene, ethyl acetate, butyl acetate, isopropyl acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetyl acetone and acetyl acetone can be used.

The solid content concentration in the coating agent is appropriately selected depending on the viscosity of the coating agent and the thickness of the adhesive layer, but is preferably 5 to 20% by mass.

Next, the above-mentioned base film is conveyed to the coater, and the coating agent for the adhesive layer is applied. Here, the surface to be coated with the adhesive layer may be either surface of the base film, but the coated surface may be pretreated with a corona treatment or the like in advance to improve the wettability with the coating agent. preferable. On the other hand, it is preferable not to perform pretreatment such as corona treatment on the back surface of the base film in order to improve releasability. The coating method (coating method) is not particularly limited, and existing coating methods such as a metabar method, a doctor blade method, a gravure method, a die method, a knife method, a reverse method, and a dip method can be adopted. However, the pressure-sensitive adhesive layer thickness of the pressure-sensitive adhesive film of the present invention is as thin as 3,000 nm or less, and the gravure method or the reverse method is preferable from the viewpoint of stably obtaining a thin coating layer.

After applying the coating agent for the pressure-sensitive adhesive layer to the base film, the film is guided to a drying furnace and the solvent in the coating material is removed to obtain a pressure-sensitive adhesive film. The drying temperature here is appropriately set depending on the heat resistance of the base film and the boiling point of the solvent, but is preferably 60 to 170 ° C. If the temperature is lower than 60 ° C., the adhesive layer may not be sufficiently cured and betrayed may occur. If it exceeds 170 ° C., the base film may be deformed and the flatness may be deteriorated. The drying time is preferably 15 to 60 seconds. If it is less than 15 seconds, the adhesive layer may not be sufficiently cured and betrayed may occur. If it exceeds 60 seconds, the productivity will decrease, which is not preferable.

The adhesive film after drying is wound with a winder without using a release film or the like to obtain an adhesive film roll of the present invention. The pressure-sensitive adhesive film of the present invention has the above-mentioned structure, so that the pressure-sensitive adhesive layer is sufficiently cured and the back surface of the base film and the surface of the pressure-sensitive adhesive layer have good slipperiness. Therefore, the pressure-sensitive adhesive film is wound without a release film. Even if it is taken, there is no problem such as line-up or wrinkles during winding, and a high-quality adhesive film roll can be obtained.

The adhesive film of the present invention obtained as described above can be used for various purposes such as packaging films, surface protective films, process films, sanitary products, agricultural products, building products, medical products, etc., but particularly on the surface. Since it is excellent in smoothness, it can be preferably used as a surface protective film or a process film.

Hereinafter, the present invention will be described in detail with reference to Examples. The characteristics were measured and evaluated by the following methods.

(1) Film Thickness Five points were measured using a microthickness meter (manufactured by Anritsu), and the average value was calculated.

(2) Thickness of Adhesive Layer 15 points were measured using the "film thickness measurement system" model number F20 of Filmometry Co., Ltd., and the average value was calculated.

(3) Film surface roughness (SRa, SRz)
Using a surface roughness meter (SURFCORDER ET4000A: manufactured by Kosaka Laboratory Co., Ltd.), measurement was performed under the following measurement conditions based on JIS-B-0601: 2001, and the average surface roughness SRa (nm) of the central surface and ten The point average roughness SRz (nm) was determined. However, the measurement was performed at three locations on the back surface of the base film (the surface on which the adhesive layer was not provided), and the average value was used.

<Measurement conditions>
Measurement speed: 0.1 mm / S
Measurement range: 1000 μm in the longitudinal direction, 400 μm in the width direction
Measurement pitch: 1 μm in the longitudinal direction, 5 μm in the width direction
Cutoff value λc: 0.2 mm
Radius of stylus tip: 0.5 μm.

(4) Peeling force The peeling force was measured in accordance with the method specified in JIS Z 0237 (2009), and a glass plate whose surface was washed with ethanol was used instead of SUS304. The adhesive films of Examples and Comparative Examples were cut into strips having a width of 25 mm and a total length of 200 mm, the adhesive layer side was attached to the glass plate, and pressed with a rubber roller having a mass of 2 kg to uniformly adhere to each other. .. After standing for 24 hours in an atmosphere of 25 ° C. and 65% RH, the glass plate is fixed and one end of the adhesive film is peeled off by measuring the stress (N / 25 mm) when peeling 180 ° at a constant speed of 300 mm / min. It was power.

(5) Haze of film The haze value (%) at 23 ° C. of the film was measured three times according to JIS K7136 (2000) using a haze meter (NDH-5000 manufactured by Nippon Denshoku Kogyo Co., Ltd.). The average value was used.

(6) Young's modulus in the longitudinal direction and the width direction ( _EMD , _ETD )
The film was cut into a rectangle having a length of 150 mm in the test direction and a length of 10 mm in the width direction as a sample. Using a tensile tester (Tencilon AMF / RTA-100 manufactured by Orientec), measure 5 times in a 25 ° C. and 65% RH atmosphere according to the method specified in JIS K7161 (1994), and obtain the average value. It was. However, the initial distance between the chucks was 50 mm, the tensile speed was 300 mm / min, and the point where the load passed 1 N after the start of the test was set as the origin of elongation.

(7) Windability evaluation Using a friction measuring instrument manufactured by Toyo Tester Kogyo, the initial rise when the back surface of the adhesive film and the adhesive layer surface are overlapped so as to be in contact with each other and rubbed against each other according to ASTM D1894. The resistance value was measured, and the maximum value was defined as the static friction coefficient μs. The sample was a rectangle having a width of 80 mm and a length of 200 mm, and two sets (4 sheets) were cut out. The measurement was performed twice, the average value was calculated, and the evaluation was made according to the following criteria.

A: μs <1.0
B: 1.0 ≤ μs <1.5
C: 1.5 ≤ μs
(8) Evaluation of betrayal Two adhesive films are sample-ringed in a square with a width of 100 mm and a length of 100 mm, and the back surface of the first adhesive film and the other adhesive layer surface are overlapped so as to be in contact with each other. Was sandwiched between two acrylic plates (width 100 mm, length 100 mm), a load of 2 kg was applied, and the film was allowed to stand for 24 hours in an atmosphere of 23 ° C. After 24 hours, the line-up when the two adhesive films were peeled off was evaluated according to the following criteria.

A: Can be peeled off cleanly B: Area where lining occurs is less than 10% C: Area where lining occurs is 10% or more.

(9) Evaluation of transfer to an adherend A pressure-sensitive adhesive film and "Zeonoa film" (registered trademark) manufactured by Nippon Zeon Co., Ltd. with a thickness of 40 μm were sample-ringed into a square with a width of 100 mm and a length of 100 mm. The films were stacked so as to be in contact with each other, sandwiched between two acrylic plates (width 100 mm, length 100 mm), loaded with a load of 2 kg, and allowed to stand for 24 hours in an atmosphere of 23 ° C. After 24 hours, the surface of the "Zeonoa film" (the surface in contact with the adhesive film) was visually observed and evaluated according to the following criteria.

A: Clean and equivalent to before applying load B: Weak unevenness is confirmed C: Strong unevenness is confirmed.

(Example 1)
As a base film, crystalline polypropylene (manufactured by Prime Polymer Co., Ltd., TF850H, MFR: 2.9 g / 10 minutes, mesopentad fraction: 0.94) was supplied to a single-screw melt extruder and melted at 240 ° C. Extrusion was performed, foreign matter was removed with a 60 μm-cut sintering filter, and the foreign matter was discharged to a casting drum whose surface temperature was controlled to 30 ° C., and the film was brought into close contact with the casting drum with an air knife. Then, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 140 ° C. using a ceramic roll, and stretched 4.6 times in the longitudinal direction of the film between the rolls at 140 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 170 ° C. for 3 seconds, stretched 8.0 times at 165 ° C., and at 150 ° C. while giving 10% relaxation in the width direction. The heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around the core to obtain a base film having a thickness of 25 μm. Table 1 shows the physical characteristics of the base film and the evaluation results.

Subsequently, an acrylic pressure-sensitive adhesive (SK Dyne (registered trademark) 1310 manufactured by Soken Kagaku Co., Ltd.) was diluted with ethyl acetate, toluene, and MEK on one side of the base film, and the solid content of the pressure-sensitive adhesive was 100 parts by mass. A coating film mixed with 2.0 parts by mass of a curing agent (Nippon Polyurethane Industry Co., Ltd., Coronate D-90) was applied using a gravure coater, dried in an oven at 80 ° C. for 30 seconds, and the adhesive layer thickness was 500 nm. The adhesive film of No. 1 was wound as it was (without using a release film) for 1,000 m to obtain an adhesive film roll. There were no wrinkles or air bites when winding the roll, and the appearance was good. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Example 2)
In Example 1, the thickness of the pressure-sensitive adhesive layer was set to 1,000 nm, and the pressure-sensitive adhesive film was wound as it was (without using a release film) for 1,000 m in the same manner as in Example 1 except for the pressure-sensitive adhesive film roll. No wrinkles occurred when winding the roll, but some air biting occurred. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Example 3 (reference example) )
In Example 1, a PET film (T60 (38 μm) manufactured by Toray Industries, Inc.) was used as the base film, the thickness of the adhesive layer was set to 300 nm, and the adhesive film was used as it was in the same manner as in Example 1 except for the above. The roll was wound up to 1,000 m (without using a release film) to form an adhesive film roll. There were no wrinkles or air biting when the roll was wound, and the appearance was good. The physical properties and evaluation results of the adhesive film are shown. Shown in 1.

(Example 4 (reference example) )
In Example 3 (reference example) , the thickness of the adhesive layer was set to 800 nm, and the adhesive film was wound as it was (without using a release film) for 1,000 m in the same manner as in Example 3 (reference example) . It was used as an adhesive film roll. No wrinkles occurred when winding the roll, but some air biting occurred. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Example 5)
90 parts by mass of crystalline polypropylene (PP (a)) (manufactured by Prime Polymer Co., Ltd., TF850H, MFR: 2.9 g / 10 minutes, mesopentane fraction: 0.94), 4-methyl-1-pentene weight The coalesced product (MX004 manufactured by Mitsui Chemicals, Inc.) is supplied as a raw material from a measuring hopper to a twin-screw extruder so that 10 parts by mass is mixed at this ratio, melt-kneaded at 260 ° C., and discharged from a die in a strand shape. Then, it was cooled and solidified in a water tank at 25 ° C. and cut into chips to obtain a polypropylene raw material (1) for the A layer.

As a polypropylene raw material for the surface layer (A), 20 parts by mass of the polypropylene raw material (1) and 80 parts by mass of the crystalline PP (a) are dry-blended and supplied to a single-screw melt extruder for the A layer. As a polypropylene raw material for the core layer (B), 100 parts by mass of the crystalline PP (a) is supplied to a single-screw melt extruder for the B layer, melt-extruded at 240 ° C., and a 10 μm-cut sintered filter. After removing foreign matter with, stack with a feed block type A / B / A composite T-die at a thickness ratio of 1/22/1, discharge to a casting drum whose surface temperature is controlled at 25 ° C, and cast drum with an air knife. It was brought into close contact with. Then, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 145 ° C. using a ceramic roll, and stretched 4.2 times in the longitudinal direction of the film between the rolls at 140 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 170 ° C. for 3 seconds, stretched 8.0 times at 165 ° C., and at 150 ° C. while giving 10% relaxation in the width direction. The heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around the core to obtain a base film having a thickness of 24 μm. Table 1 shows the physical characteristics of the base film and the evaluation results.

Subsequently, an acrylic pressure-sensitive adhesive (manufactured by Soken Kagaku Co., Ltd., "SK Dyne" (registered trademark) 1310) was diluted with ethyl acetate, toluene, and MEK on one side of the base film to make 100 parts by mass of the solid content of the pressure-sensitive adhesive. On the other hand, a coating film mixed with 2.0 parts by mass of a curing agent (Coronate D-90 manufactured by Nippon Polyurethane Industry Co., Ltd.) was applied using a gravure coater, dried in an oven at 80 ° C. for 30 seconds, and adhered to the adhesive layer. The adhesive film having a thickness of 300 nm was wound as it was (without using a release film) for 8,000 m to obtain an adhesive film roll. There were no wrinkles or air bites when winding the roll, and the appearance was good. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Example 6)
In Example 1, the temperature of the casting drum was set to 50 ° C., the thickness of the adhesive layer was set to 600 nm, and the adhesive film was wound as it was (without using a release film) by the same method as in Example 1 for 1,000 m. , Adhesive film roll. There were no wrinkles or air bites when winding the roll, and the appearance was good. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Comparative Example 1)
In Example 1, the thickness of the adhesive layer was set to 4,500 nm, and the adhesive film was wound as it was (without using a release film) for 1,000 m in the same manner as in Example 1 to form a film roll. Wrinkles occurred when winding the roll, and it was not possible to wind it with good quality. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Comparative Example 2)
In Example 3 (reference example) , the thickness of the adhesive layer was set to 4,500 nm, and the adhesive film was wound as it was (without using a release film) for 1,000 m in the same manner as in Example 3 except for the film roll. And said. Wrinkles occurred when winding the roll, and it was not possible to wind it with good quality. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

(Comparative Example 3)
In Example 1, the temperature of the cast drum was set to 70 ° C., the thickness of the adhesive layer was set to 600 nm, and the adhesive film was wound as it was (without using a release film) by the same method as in Example 1 for 1,000 m. , Adhesive film roll. There were no wrinkles or air bites during roll winding, and the appearance was good, but no adhesive strength was exhibited. Table 1 shows the physical characteristics of the adhesive film and the evaluation results.

Claims (8)

An adhesive film in which an adhesive layer is provided on one side of a base film containing polypropylene as a main component, and a ten-point average roughness SRz of the back surface (the surface without the adhesive layer) of the base film is 3,000 nm or less. An adhesive film having an adhesive layer having a thickness d of 3,000 nm or less. The adhesive film according to claim 1, wherein the central surface average surface roughness SRa of the back surface of the base film is 100 nm or less. The pressure-sensitive adhesive film according to claim 1 or 2, wherein the ratio of the ten-point average roughness SRz on the back surface of the base film to the thickness d of the pressure-sensitive adhesive layer and the value of SRz / d are 0.1 to 3.5. The adhesive film according to any one of claims 1 to 3, wherein the thickness d of the adhesive layer is 600 nm or less. The adhesive film according to any one of claims 1 to 4 , wherein the base film is mainly composed of crystalline polypropylene having a mesopentad fraction of 0.90 or more. The adhesive film according to any one of claims 1 to 5 , wherein the haze is 10% or less. The adhesive film according to any one of claims 1 to 6 , wherein the peeling force at 180 ° C. after being bonded to a glass plate is 1 N / 25 mm or less. An adhesive film roll obtained by winding the adhesive film according to any one of claims 1 to 7 without using a release film.